Let first 6 pups be seated. Now among the seven spaces available between pups (5 in between and 2 on either ends), we need to select 4 for the cats. No of ways to arrange 4 cats in 7 places = 7C4. So required number of ways are C(7, 4)*4!*6! = 6!*P(7, 4) i.e. option c.